Archives

As Loran Fades, Attention Shifts to DGPS and SBAS

November 30, 2009 - By

Few precise-positioning users have employed Loran in a professional sense, although maybe you have in your personal life if you’re a airplane pilot or a mariner. Then again, if you've flown as an airline passenger or cruised onboard a ship, you've benefited from the back-up to GPS that Loran provides. That back-up is about to go away. As attention and resources shift away from Loran, they focuses more intensely on GPS augmentations, specifically differential GPS (DGPS) and satellite-based augmentation systems (SBAS) such as WAAS and EGNOS. read more

This article is tagged with and posted in Newsletter Editorials, Opinions, Survey, Survey Scene

A Little Q&A Follow-up and Feedback on My Last Column

November 19, 2009 - By

I received some feedback on my last column entitled "What’s the Difference Between a Used Car Salesman and a GPS Salesman?" Most of the comments were positive in that the technical content was reasonably deep and thorough. However, I did receive a couple of e-mails from folks who were offended by the comparison. read more

This article is tagged with and posted in Newsletter Editorials, Opinions, Survey, Survey Scene

What’s the Difference between a Used Car Salesman and a GPS Salesman?

November 3, 2009 - By

I didn’t attend the Minnesota GIS/LIS Annual Conference last week, but I received a report from someone who attended a session in which the presenter seemed to fit the maxim quite well. One of the presenter’s messages was that people should stop using WAAS immediately as a GPS correction source due to the inability of data collection software to handle the ITRF00 > NAD83/CORS96 datum shift. Following is a statement from one of his slides… read more

This article is tagged with and posted in Newsletter Editorials, Opinions, Survey, Survey Scene

The System: Galileo Slips, EGNOS Operates

November 1, 2009 - By

Four Galileo in-orbit validation (IOV) satellites scheduled to launch next year have already missed their first pad date.The European version of Russia’s Soyuz rocket is now scheduled to carry the four IOV satellites into orbit in two launches in November 2010 and early 2011, as announced by European Space Agency (ESA) Director-General Jean-Jacques Dordain on October 9. Both launches had... read more

The True Story of the Origins of GPS

November 1, 2009 - By

Photos from the GPS World Leadership Dinner 2009, September 24 ION GNSS 2009 Conference, Savannah, Georgia read more

This article is tagged with , and posted in GNSS, OEM

Expert Advice: GPS Constellation Maxed Out at 30

November 1, 2009 - By

It appears that the GPS satellite constellation has a glass ceiling, so to speak. GPS was designed as a 24-satellite constellation, with four satellites in six orbital planes arranged to provide maximum observability around the globe. According to the government’s Space-Based Positioning, Navigation, and Timing website, “The U.S. government is committed to provide a minimum of 24 operational GPS satellites on orbit, 95 percent of the time. The U.S. Air Force launches additional satellites that function as active spares to accommodate periodic satellite maintenance downtime and assure the availability of at least 24 operating satellites. As of August 28, 2009, there were 35 satellites in the GPS constellation, with 30 set ‘healthy’ to users.” read more

This article is tagged with and posted in Expert Advice & Leadership Talks, GPS Modernization

Out in Front: An SVN up for Grabs

November 1, 2009 - By

Wednesday evening, September 23, Savannah, Georgia, 5:30 to 7:00 p.m., Session P2b — a date that will live in GPS history. The 400 to 600 of us who were there to witness it will never forget it. The SVN49 Review Panel. Unprecedented puts it mildly. read more

This article is tagged with and posted in From the Editor

Higher Timing Accuracy, Lower Cost

November 1, 2009 - By

Inside a typical GNSS receiver, the estimate of the error in the local oscillator is formed as a component of the navigation solution, which is in turn based on the output of each satellite-tracking channel propagating its estimate of carrier and code measurements to a common future point. But this method limits the resolution with which the noise of the local oscillator can be quantified. To bypass this shortcoming requires a method of coherently gathering information about the phase change in the local oscillator across all available satellite signals: to use the same samples simultaneously for all satellites in view to estimate the center-point phase error common across the visible constellation. We explore how. read more

This article is tagged with and posted in Receiver Design, Simulators & Tools, Timing